1. Field of the Application
The present application relates to an axial turbomachine rotor. More specifically, the present application relates to a system for damping vibrations of an axial turbomachine rotor. More specifically, the present application relates to a system for damping vibrations of bladed wheels of an axial turbomachine rotor with a dissipative electric circuit.
2. Description of Related Art
During operation, annular heterogeneous flows pass through an axial turbomachine. In fact, any body located in an axial homogeneous flow will generate variations of aerodynamic pressure in the surrounding environment thereof, thus making the flow heterogeneous. These bodies may be, inter alia, blades, case struts, or variable discharge gates.
When a blade of a bladed rotor turns in an annular flow having such circumferential heterogeneities, each sudden variation of pressure will be considered as a punctiform excitation. The number of excitations over 360° associated with a given speed of rotation results in a particular excitation frequency. If this corresponds to a natural frequency of the rotor, the rotor will then enter into resonance in accordance with a particular mode of deformation composed of a certain number of nodal diameters.
When the bladed rotor wheel enters into resonance over a particular mode of deformation, increased vibratory levels develop. These vibratory levels will be greater, the weaker the intrinsic damping level of the structure, for example in the case of blisks or one-piece bladed drums. Such vibratory levels are to be avoided since they are associated with high stress states, which significantly reduce the fatigue life of the structure and may lead to the destruction thereof. In this context, the use of damping devices may prove indispensible in order to ensure the fatigue resistance of the bladed wheel.
Among the damping devices conceivable for the bladed turbomachine rotor wheels subjected to a diameter deformation, a shunted piezoelectric system represents an interesting solution. This is formed is a piezoelectric patch connected to a dissipative electric circuit.
Document JP19960861295 discloses a bladed rotor of which the vibrations are reduced with the aid of piezoelectric patches distributed over the periphery of said rotor. Each patch is connected to a closed circuit comprising a dissipative resistor. The operating principle lies in the existence of deformations at the same location of the piezoelectric patches, which, once deformed, generate a current dissipated by the resistors of the connected circuit. This damping method makes it possible to reduce the vibrations of a rotor and brings the same efficacy for each frequency. However, this damping method is ineffective for a vibration of strong amplitude. This system also involves providing each closed circuit with components, thus increasing mass and cost. The necessary space for installing each circuit is disadvantageous.
Although great strides have been made in the area of damping vibrations of an axial turbomachine rotors, many shortcomings remain.